autotools, cmake: set SDL_SYSTEM_ICONV to OFF for windows (like SDL3.)

CMakeLists.txt

@@ -241,6 +241,11 @@ endif()
 if(UNIX OR MINGW OR MSYS OR (USE_CLANG AND NOT WINDOWS) OR VITA OR PSP OR PS2 OR N3DS)
   set(OPT_DEF_LIBC ON)
 endif()
+if(WINDOWS)
+  set(SDL_SYSTEM_ICONV_DEFAULT OFF)
+else()
+  set(SDL_SYSTEM_ICONV_DEFAULT ON)
+endif()
 
 if(NOT ("$ENV{CFLAGS}" STREQUAL ""))
   if(CMAKE_VERSION VERSION_LESS 3.11.0)
@@ -420,7 +425,7 @@ set_option(SDL_DIRECTFB            "Use DirectFB video driver" OFF)
 dep_option(SDL_DIRECTFB_SHARED     "Dynamically load directfb support" ON "SDL_DIRECTFB" OFF)
 set_option(SDL_DUMMYVIDEO          "Use dummy video driver" ON)
 dep_option(SDL_IBUS                "Enable IBus support" ON ${UNIX_SYS} OFF)
-set_option(SDL_SYSTEM_ICONV        "Use iconv() from system-installed libraries" ON)
+set_option(SDL_SYSTEM_ICONV        "Use iconv() from system-installed libraries" ${SDL_SYSTEM_ICONV_DEFAULT})
 set_option(SDL_LIBICONV            "Prefer iconv() from libiconv, if available, over libc version" OFF)
 set_option(SDL_OPENGL              "Include OpenGL support" ON)
 set_option(SDL_OPENGLES            "Include OpenGL ES support" ON)